Well the Stall Current is close to what is calculated with Ohm's Law and a measurement of the DC resistance of the motor winding. This would be the maximum current the motor will draw and a good rule of thumb for sizing the driver.

The no load current can be measured by putting a low value resistor is series with the motor and battery. Measure the voltage drop across the resistor and calculate the current with Ohm's law. Chose a resistor value to get around 0.1 to 0.3 Volt drop.